NAVARACHANA UNIVERSITY

SELF LEARNING MATERIAL

PLANT TISSUE

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PLANT TISSUE

1. Tissue is a group of cells having similar origin, structure& function. Study of tissues is called Histology

2. In unicellular organism (Amoeba) single cell performs all basic functions, whereas in multi-cellular organisms (Plants and Animals) shows division of labor as Plant tissue & Animal tissues.

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Plant tissues are two types: Meristems & Permanent tissues.

Meristems: The Meristems are the tissues having the power of cell division. It is found on those regions of the plant which grows

Types of Meristems;

1. The Apical meristems – It is present at the growing tip of the stem and roots and increases the length.

2. The lateral meristems - present at the lateral side of stem and root (cambium) and increase the girth.

3. The intercalary meristems - present at internodes or base of the leaves and increase the length between the nodes.

Permanent tissues: Two types such as Simple permanent tissues & Complex permanent tissues.

a) Simple permanent tissues: subdivided as

(i): Parenchyma: Tissues provide the support to plants. They are loosly packed and have large intracellular space.

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- Parenchyma with chlorophyll which performs photosynthesis is called as chlorenchyma.

- The parenchyma with large air spaces to give buoyancy is called as aerenchyma. Parenchyma also stores food and water.

(ii) Collenchyma: Tissue provides mechanical support, thickened at the corners, have very little intercellular space. It allows easy bending of various parts of plants without breaking

(iii) Sclerenchyma: Tissue makes the plant hard and stiff, thickened due to lignin and no intercellular space.

Cells of this tissue are dead and commonly seen in the husk of

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coconut.

(iv) Guard cells and epidermal tissue: The tissue aids in protection and exchange of gases. Guard cells kidney shaped in dicots, dumb bell shaped in monocots to guard the stomata.

The epidermal tissues of roots aid in absorption of water and minerals.

The epidermal tissues in desert plants have a thick waxy coating of Cutin with waterproof quality.

The epidermal tissues form the several layer thick Cork or the Bark of the tree.

Epidermis: Epidermis forms one cell thick outermost layer of various body organs of plants such as leaves, flowers, stems and roots. 

Epidermis is covered outside by cuticle. Cuticle is a water proof layer of waxy substance called as cutin which is secreted by the epidermal cells. Cuticle is very thick in xerophytes. 

Cells of epidermis of leaves are not continuous at some places due to the presence of small pores called as stomata. Each stoma is guarded by a pair of bean shaped cells called as guard cells. These are the only epidermal cells which possess chloplasts, the rest being colorless.

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Functions :(i) The main function of epidermis is to protect the plant from desiccation and infection.

(ii) Cuticle of epidermis cuts the rate of transpiration and evaporation of water and prevents wilting.

(iii) Stomata in epidermis allow gaseous exchange to occur during photosynthesis respiration.

(iv) Stomata also helps in transpiration.

Cork or phellem : in older roots and stems, tissues at the periphery become cork cells or phellem cells. 

Cork is made up to dead cells with thick walls and do not have any intercellular spaces. The cell walls in cork deposit waxy substance called as suberin. 

The cells of cork become impermeable to water and gasses due to the deposition of suberin. The cork cells are without any protoplasm but are filled with resins or tannins.

Functions:

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(i) Cork is protective in function. Cork cells prevent desiccation, infection and mechanical injury.

(ii) Imperviousness, lightness, toughness, compressibility and elasticity make the cork commercially valuable.

(iii) Cork is used for insulation, as shock absorber in linoleum. 

(iv) Cork is used in the making of a variety of sport goods such as cricket balls, table tennis, shuttle cocks, wooden paddles etc.

b) Complex permanent tissues: The complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function.

They are subdivided as;

Xylem: It consists of tracheids, vessels, xylem parenchyma and xylem fibers. The cells have thick walls,

Function - aids in conduction of water and minerals.

Phloem: It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers.

Function - Phloem transports food material to other parts of the plants..

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ACTIVITY. Plant Tissue Systems;The tissues of a plant are organized into three tissue systems: the dermal tissue system, the ground tissue system, and the vascular tissue system.Use information from the table to answer the questions below it.Tissue Systemand Its Functions

Component Tissues

Location of Tissue Systems

Dermal Tissue System• protection• prevention of water loss

EpidermisPeriderm (in older stems and roots)

Ground Tissue System• photosynthesis• food storage• regeneration • support• protection

Parenchyma tissueCollenchyma tissueSclerenchyma tissue

Vascular Xylem tissue

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Tissue System• transport of water and minerals• transport of food

Phloem tissue

1. Where is the vascular tissue system located in roots?

2. Where is the ground tissue system located in a (dicots) stem?

3. What type of tissue are the veins in leaves?

4. Name three tissues in the ground tissue system.

Activity:Basic Plant StructurePlants have three vegetative organs: roots, stems,

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and leaves.Use information from the illustration to answer the questions below.1. Which part of the leaf has the main function to carry out photosynthesis?

2. The petiole is part of which plant organ?

3. Where on the stem are the axillary buds attached?

4. From what plant part does the shoot develop?

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Activity:Ground TissuesThe three types of ground tissue, parenchyma, collenchyma, and sclerenchyma, function in photosynthesis, storage, regeneration, support, and protection.Use information from the table to help answer the questions below it.

Ground Tissue

Parenchyma Tissue Collenchyma Tissue

Sclerenchyma Tissue *

Function • Photosynthesis• Food storage• Healing and tissue regeneration

• Support in young stems, roots, and petioles

• Rigid support• Protection

Cell Types in This Tissue

Parenchyma cells Collenchyma cells Sclereid cells & fiber cells

*Some texts include tracheids and vessels as components of sclerenchyma tissue.

1. Potatoes contain food in the form of starch, which ground tissue are you eating when you eat mashed potatoes?

2. The part of rhubarb that people eat is the petiole of a large leaf. Which tissue provides support for rhubarb?

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3. Which ground tissue is a major component of the blades of spinach leaves?

4. Which ground tissue makes the shell of a nut hard?

ACTIVITY:Vascular TissuesVascular tissue is composed of xylem and phloem, which function in the transport of water and dissolved substances.Use the information in the table to help answer the questions below it.

Vascular Tissue

Xylem Tissue Phloem Tissue

Function • Conduct water and dissolved minerals• Support

• Conduct food and other organic substances

Cell Types Unique to This Tissue

Tracheids Vessel members Companioncells

Sieve-tubeelements

Additional Cell Types in This

Parenchyma cellsFibers

Parenchyma cellsFibers

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Tissue

1. Which tissue is most likely to transport dissolved sugar?

2. What tissue transports water through dead cells?

3. Companion cells are unique to which tissue?

4. Vessel members are unique to which tissue?

ACTIVITY :Primary Growth of StemsThe apical meristem produces the three primary meristems, protoderm, procambium, and ground meristem, which develop into dermal tissues, vascular tissues, and ground tissues respectively.Use the information in the illustration to help answer the questions below it.

1. Xylem and phloem tissues are derived from which primary meristem?

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2. What is the dermal tissue called that is found in young stems and roots?

3. From which primary meristem is the epidermis derived?

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ACTIVITY:Primary Growth of RootsIn roots, the three primary meristems, protoderm, procambium, and ground meristem, develop from the apical meristem and differentiate into epidermis, vascular tissues, and ground tissues.Label the longitudinal section of a root below. On the left, label the regions in which cell division, cell elongation, and cell differentiation take place. On the right, label the apical meristem, the three primary meristems, and the three primary tissues. Click on the Check Your Answers button to compare your answer with the correct answers.

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EXERCISE:1. Primary tissues arise:

a.during secondary growth

b.from the three primary meristematic tissues

c.from the vascular cambium

d.from the cork cambium

e.from two of the above

2. Secondary growth:

a.occurs in all angiosperms

b.is accomplished by the procambium

c.is accomplished, at least in part, by the vascular cambium

d.brings about an increase in the height of the plant

e.results in the formation of the endodermis

3. The tissue most likely to provide flexible support is the:

a.epidermis

b.sclerenchyma

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c.parenchyma cell

d.collenchyma

e.cambium

4. Cells which are typically in xylem but not in other plant tissues are:

a.tracheids

b.vessel elements

c.both tracheids and vessel elements

d.neither tracheids nor vessel elements

e.companion cells

5. The secondary cell walls of adjacent cells:

a.lie in direct contact with one another

b.are separated from one another by the middle lamella

c.are separated from one another by the primary walls and the middle lamella

d.are formed following the death of the cells

e.play no significant role in cell function

6. Mature sieve-tube members lack:

a.cell walls

b.cell membranes

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c.cytoplasm

d.nuclei

e.sieve plates

7. The increase in diameter of the trunk of a tree is produced primarily by the:

a.apical meristem

b.cork cambium

c.pith

d.vascular cambium

e.cork

8. In a three-year-old stem, the oldest secondary xylem is found:

a.adjacent to the pith

b.just inside the vascular cambium

c.just outside the vascular cambium

d.immediately adjacent to the primary phloem

e.immediately adjacent to the secondary phloem

9. In a twenty-year-old woody stem:

a.the most abundant tissue would be the secondary xylem

b.the most abundant tissue would be the secondary phloem

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c.secondary xylem and secondary phloem would be equally abundant

d.the most abundant tissue would be the cork

e.the oldest vascular cambium would be inactive

10. The tissue formed on the outside of a woody stem is called:

a.bark

b.cork

c.cortex

d.secondary phloem

e.endodermis

11. Root hairs:

a.are multicellular filaments

b.are epidermal cells

c.arise from the endodermis

d.function in support

e.two of the above

12. The apical meristem in the root:

a.is located behind the root cap

b.produces cells which become incorporated into the root cap

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c.gives rise to the primary meristematic tissues

d.is a region of active cell division

e.all of the above

13. In a young root, the sequence of tissues from the outside to the center is:

a.epidermis, pericycle, cortex, endodermis, primary phloem, primary xylem

b.epidermis, cortex, endodermis, pericycle, primary phloem, primary xylem

c.epidermis, cortex, primary phloem, primary xylem, endodermis, pericycle

d.epidermis, primary phloem, cortex, primary xylem, endodermis, pericycle

e.epidermis, cortex, pericycle, endodermis, primary phloem, primary xylem

14. In the root, the pericycle:

a.is a single layer of cells just inside the epidermis

b.arises from the ground meristem

c.arises from the procambium

d.is situated between the primary xylem and primary phloem

e.regulates the movement of materials into the vascular tissue

15. The structure in the leaf that regulates water loss and gas exchange is the:

a.cuticle

b.epidermis

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c.palisade mesophyll

d.spongy mesophyll

e.Stoma

By NEELAM KUSHWAHA